In order to understand the regulation of the transcription and translation of C Mu and C Delta immunoglobulin genes, we plan to first evaluate the rate of synthesis of mRNA for Mu and Delta chains in a B lymphoma cell line BCL1, which expresses both isotypes. Secondly, since BCL1 cells can be induced to differentiate to immunoglobulin secretion by stimulation with lipopolysaccharide (LPS), we will also measure the effect of this perturbance of the steady state on the rate of mRNA synthesis for the two species. Thirdly, we will examine the rates of IgM and IgD synthesis before and after LPS stimulation to determine whether translational and/or post-translational control also play a role in the regulation of the synthesis of these two isotypes. Finally, as a first step towards analysis of the termination and/or processing enzymes involved in producton of the various mature Mu and Delta mRNA species, experiments will be conducted to detect the primary transcriptional products of C Mu and C Delta genes. The results of these experiments should contribute significantly towards our understanding of the relationship of the two transcriptional units and the effect of B cell activation on these units.